As the denitration catalyst for ammonia catalytic reduction, containing titanium oxide as a main component has high activity and favorable durability, it is generally used worldwide for the treatment of exhaust gas such as gas released from a boiler and constitutes the mainstream denitration catalyst (Patent Document 1).
In recent years, there is a rapid increase in demand for energy and coals having high sulfur content (i.e., high S coals) start to be used as fuel. In addition to this, a trouble caused by SO3 increases, for example, part of SO2 is oxidized to SO3 due to a SO2 oxidizing activity of a denitration catalyst so that visible stack plumes originating from SO3 is released from a stack or a downstream equipment in a denitration apparatus is corroded, etc. As such, in accordance with increased needs for a denitration catalyst having very low SO2 oxidizing activity, a catalyst with modified composition (Patent Document 2) and a catalyst having a distribution in concentration of the catalyst components (Patent Document 3) are known.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 50-128681    Patent Document 2: JP-A No. 2-184342    Patent Document 3: JP-A No. 09-220468